As illustrated in FIG. 1, it has become contemporary practice to package products 10, for example foodstuffs, medicines, disposal medical devices, in packages indicated by 20, wherein each package includes a base 30, optionally with a recess, to receive the product 10, and a cover 40 which is sealed via a seal 50 to the base 30 to enclose the product 10. For certain categories of product 10, for example medical products which must remain in a sterile environment prior to being used, the seal 50 is beneficially airtight so that the product 10 is retained in a hermetically-sealed or antiseptic environment. Moreover, the seal 50 is conventionally implemented in several different manners, depending upon requirements, for example using adhesives, by heating, by welding and so forth. The seal 50 is required to be sufficiently mechanically strong to withstand handling of the packaging 20. Contemporary examples of packaging are manufactured, for example, by a DuPont, for example in association with its registered trade mark Tyvek® as reported at a web-site:
http://www2.dupont.com/Medical_Packaging/en_US/products/index.html
It is important that the seal 50 is reliable, for example potentially over a period of many years when packages are in storage and are awaiting to be deployed, for example as emergency medical supplies to be deployed in disaster zones around the World. A fault or failure of the seal 50 in a context of medical products stored in a package 20 can potentially be fatal, because a broken seal may potentially result in contamination, for example bacteria, mould, entering into the package 20. Moreover, in relation to food products, food stored in the package 20 can become rotten or spoiled, rendering it dangerous for consumption, if its seal 50 is not properly formed.
In a packaging line, along which products 10 are placed and sealed into corresponding packages 20, it is well known to employ inspection apparatus including one or more cameras linked to computing hardware executing image processing software to view the packages 20 after their seals 50 have been formed, wherein the computing hardware executes one or more algorithms to process images of the seals 50 for determining whether or not the seals 50 have been correctly formed, for example to be devoid of bubbles, occlusions, debris, moisture and such like. Such known inspection apparatus is described in published patent applications, for example:
DocumentDetailJP4523474B2“Defect inspection device and PTP packagingmachine”, Applicant CKDU.S. Pat. No. 7,142,707“Automated inspection of packaging materialsfor package integrity”, Applicant NorthropGrumman
Common and conventional seal Integrity testing and inspection procedure used widely in medical industry is described in the ASTM Standard <<Standard Test Methods for Detecting Seal leaks in Porous Medical Packaging by Dye Penetration>>, Designation: F1929-98 (Reapproved 2004). This procedure is based on dye penetration: Dye is injected with a dispenser to inside the package and the seal is then inspected visually if there are channels etc. visible in the seal area. The disadvantages of this method are: It is very time consuming, and it destroys the package.
A problem encountered, when employing image processing of packages 20 for determining integrity of their seals 50, is that computer-automated inspection of the seals 50 is time-consuming and requires considerable costly computing capacity for its implementation. Additionally, camera based imaging systems with conventional illumination and imaging solutions yield very poor contrast for the package seal area. Heat seals have very poor contrast and it is difficult to build a reliable image processing algorithm to investigate seal integrity. For a manufacturing environment where the packages 20, with their products 10 enclosed, are produced in great numbers, employing aforesaid computer-automated inspection of the seals 50 causes an undesirable limit on feasible production rate of the packages 20, namely causes a “bottle neck” in a packaging production environment. Employing numerous inspection apparatus in parallel to resolve such a “bottle-neck” represents an expensive solution. It has thus become established conventional practice to sample packages 20 from a packaging line at intervals and then inspect the sample packages 20 for quality of their seals 50, assuming that the sample packages 20 are representative of all packages 20 being processed along the packaging line.
Alternative approaches to inspect seals 50 have been proposed. For example, in a published United States patent application no. US2012/0206710 (“Measuring instrument and method for determination of the properties of an item and its surface”, Applicant Tutkimuskeskus VTT), there is described a measurement device as indicated generally by 100 in FIG. 2. The measurement device 100 is operable to determine characteristics of an object's surface 110 by means of optical radiation, wherein the measurement device 100 comprises an optical radiation source 120 which is operable to illuminate the surface 110 and a detector 130 which is operable to receive radiation which is reflected from the surface 110. Moreover, the measurement device 100 includes an emitted optical radiation unit 140 which is operable to split optical radiation emitted by the optical radiation source 120 into separate wavelengths components and to direct the separate wavelength components to the surface 110 in a direction which is non-orthogonal to a plane of the surface 110, for example at an inclined angle as illustrated, so that shortest and longest wavelength components are focused on different portions and at different heights on the surface 110. Furthermore, the measurement device 100 includes a reflected optical radiation processing unit 150, which is operable to receive reflected optical radiation from the surface 110, at least in a direction of specular reflection, and provide the received radiation to the aforesaid detector 130. The measurement device 100 further includes computing hardware 160 for analyzing an electrical signal generated by the detector 130 in response to receiving reflected radiation thereat.
The computing hardware 160 is operable to determine a surface gloss measurement of the surface 110 and/or thickness measurements of the surface 110, based on the relative intensity of the wavelength components reflected from various points on the surface 110.
A problem encountered in practice is that aforesaid measurement devices 100, for example as illustrated in FIG. 2, are capable of being used to make measurements of surfaces 110, but are not ideal for checking seals 50 of packages 20, for example for detecting occluded air bubbles, debris and similar in manufacturing line environment.